1. Field of the Invention
This invention relates to analyte test instruments that perform electrochemical assays on biological samples. More particularly, the invention relates to analyte test instruments having improved calibration and communication processes.
2. Discussion of the Art
An analyte test instrument can be used to perform electrochemical assays (e.g., glucose concentration) on biological samples (e.g., blood). To operate such an instrument, a user inserts a test strip into a test port in the instrument. The instrument displays a xe2x80x9creadyxe2x80x9d indication to the user and waits for the user to deposit a biological sample on the test strip. When a sufficient quantity of material is deposited on the reaction area of the test strip, an electrochemical reaction occurs. The electrochemical reaction causes a flow of electrons, which produces an electrical signal, such as a change in current, detectable by the instrument. The instrument converts the detected signal into data that corresponds to analyte information and displays the information to the user. The instrument may have the capability to store a plurality of such measurements and provide this information to the user via a display or to an external processor via a data link.
Analyte test instruments for electrochemical assays often require the user to use periodically calibrate the instrument. One known calibration technique is described in U.S. Pat. No. 5,366,609 to White et al. The disclosed instrument requires a removably insertible read-only-memory (ROM) key for operation and calibration of the instrument. The ROM key is inserted into a port, which is distinct from the test port, and must remain in the instrument during operation and calibration testing. A test strip is inserted into the test port after the ROM key is inserted into the ROM key port. The ROM key contains batch-specific constants and data required for carrying out analyte determination procedures on biological material applied to the test strips. In addition, the ROM key can contain some or all of the code that controls the testing. A microprocessor in the instrument uses the constants, conversion factors, and code provided by the ROM key on an xe2x80x9cas-needed basisxe2x80x9d to perform tests.
Another calibration technique is employed by the PRECISION Q.I.D blood glucose testing system manufactured and sold by MEDISENSE, Inc., Bedford Mass. The instrument has a single port that separately receives both calibration strips and test strips. A calibration strip including data and constants specific to a given batch of test strips, including the batch code for the test strips, is provided with each batch of test strips. Typically, when a new box of test strips is opened, the user first inserts the calibration strip into the test port to calibrate the instrument. The user then removes the calibration strip, and the instrument is ready to receive test strips. The instrument stores the batch code for the calibration strip and displays that code to the user. Thus, the user can manually verify that the batch code matches the code printed on each test strip being used. The calibration data for the instrument is specific to those test strips having the same batch code and remains stored in the instrument until another calibration strip is inserted.
Although manufacturers of analyte test instruments take great care in providing accurate calibration devices and detailed instructions on the calibration process, errors attributable to the calibration process frequently contribute to erroneous test readings. For example, known instruments do not alert the user to prevent running a test with a test strip that is not matched to the calibration of the instrument or with a test strip that has expired. In addition, known instruments do not have the capability of performing a multiplicity of different assays with a single measuring apparatus having a broad spectrum of testing functionalities without having to manually reconfigure the instrument.
The present invention provides an analyte test instrument having improved calibration and communication processes. These improved processes allow greater ease in calibration, greater ease in operation, and greater versatility. The processes also provide more reliable results than do presently available instruments.
In one aspect, the invention features a calibration method for an analyte test instrument that uses one of a plurality of data storage strips. The data storage strips can include one or more memory devices, such as a ROM device, that stores calibration and test data. The analyte test instrument includes a test port adapted to receive any one of a plurality of data storage strips, a processor electrically connected to the test port, and a memory storing a protocol for communicating with each data storage strip. The instrument receives a data storage strip in the test port. The instrument polls the test port to identify the data storage strip. When the data storage strip has been identified, the instrument establishes communications with the data storage strip using the protocol that corresponds to the data storage strip.
In one embodiment, data from the data storage strip is downloaded by the instrument and stored in the memory. The data can comprise instrument parameters (e.g., language and instrument type), test strip parameters (test strip count and expiration date), and analyte parameters. The data storage strip is removed from the test port, and a test strip can be inserted in the test port. Using the downloaded data, the instrument implements a test procedure to perform an analyte test when biological material is supplied, such as when a user provides a sample.
In another aspect, the invention provides a method for ensuring that an analyte test instrument is operated using valid calibration and test strips. The instrument includes a test port adapted to receive a calibration strip or a test strip, a processor electrically connected to the test port, a memory storing a plurality of test parameters, and a display for displaying information to a user. The instrument receives into the test port a calibration strip or a test strip. The processor accesses the test parameters stored in the memory to determine whether one or more of the test parameters is invalid for the test strip. If a test parameter is invalid, an indication of the invalid test strip parameter is displayed on the display.
In one embodiment, the test parameters can include test strip count and expiration date, instrument language, and instrument type. In some embodiments, the processor disables the instrument when certain parameters are invalid. In other embodiments, a warning is displayed when certain parameters are invalid.
In yet another aspect, the invention features a method for determining the actual date and time of events in a battery-operated analyte test instrument. Events generated by operation of the battery-operated analyte test instrument are stored in the memory. A value is assigned to each event when such event is stored in the memory. At some point, a reference date and time are provided to the battery-operated analyte test instrument (e.g., these are entered via the user interface). A reference value is assigned to the reference date and time. The actual date and time of each event are computed by adjusting the value assigned to each event using the reference value.
In still another aspect, the invention provides a method for controlling the operation of an analyte test instrument. A data storage strip is received into the test port and is polled to identify its type. Communications are established with the data storage strip, using the protocol corresponding to the data storage strip, when the data storage strip is identified. Data is then downloaded from the data storage strip into the analyte test instrument, and the analyte test instrument stores the data even after the data storage strip is removed. In some embodiments, the downloaded data comprises at least a portion of a test procedure that the analyte test instrument uses to perform diagnostic tests. In another embodiment, the analyte test instrument has stored on it a plurality of test procedures used to conduct one or more diagnostic tests using the analyte test instrument. In this embodiment, a control procedure that selects one or more of the stored procedures to run is downloaded. In this manner, the data storage strip can reconfigure the analyte test instrument xe2x80x9cin the fieldxe2x80x9d to run different types of tests or combinations of tests.